1. Field of the Invention
The invention is generally directed to devices and methods for the delivery of remotely detectable markers to a desired location within a patient's body. In particular, the invention is directed to devices and methods configured to retain a remotely detectable marker within a delivery device before delivery to a desired intracorporeal location.
2. Description of the Related Art
In diagnosing and treating certain medical conditions, it is often desirable to mark a suspicious body site for the subsequent taking of a biopsy specimen, for delivery of medicine, radiation, or other treatment, for the relocation of a site from which a biopsy specimen was taken, or at which some other procedure was performed. As is known, obtaining a tissue sample by biopsy and the subsequent examination are typically employed in the diagnosis of cancers and other malignant tumors, or to confirm that a suspected lesion or tumor is not malignant. The information obtained from these diagnostic tests and/or examinations is frequently used to devise a therapeutic plan for the appropriate surgical procedure or other course of treatment.
In many instances, the suspicious tissue to be sampled is located in a subcutaneous site, such as inside a human breast. To minimize surgical intrusion into a patient's body, it is often desirable to insert a small instrument, such as a biopsy needle, into the body for extracting the biopsy specimen while imaging the procedure using fluoroscopy, ultrasonic imaging, x-rays, magnetic resonance imaging (MRI) or any other suitable form of imaging technique. Examination of tissue samples taken by biopsy is of particular significance in the diagnosis and treatment of breast cancer. In the ensuing discussion, the biopsy and treatment site described will generally be the human breast, although the invention is suitable for marking biopsy sites in other parts of the human and other mammalian body as well.
Periodic physical examination of the breasts and mammography are important for early detection of potentially cancerous lesions. In mammography, the breast is compressed between two plates while specialized x-ray images are taken. If an abnormal mass in the breast is found by physical examination or mammography, ultrasound may be used to determine whether the mass is a solid tumor or a fluid-filled cyst. Solid masses are usually subjected to some type of tissue biopsy to determine if the mass is cancerous.
If a solid mass or lesion is large enough to be palpable, a tissue specimen can be removed from the mass by a variety of techniques, including but not limited to open surgical biopsy, a technique known as Fine Needle Aspiration Biopsy (FNAB) and instruments characterized as “vacuum assisted large core biopsy devices”.
If a solid mass of the breast is small and non-palpable (e.g., the type typically discovered through mammography), a vacuum assisted large core biopsy procedure is usually used. In performing a stereotactic biopsy of a breast, the patient lies on a special biopsy table with her breast compressed between the plates of a mammography apparatus and two separate x-rays or digital video views are taken from two different points of view. A computer calculates the exact position of the lesion as well as depth of the lesion within the breast. Thereafter, a mechanical stereotactic apparatus is programmed with the coordinates and depth information calculated by the computer, and such apparatus is used to precisely advance the biopsy needle into the small lesion. The stereotactic technique may be used to obtain histologic specimens. Usually at least five separate biopsy specimens are obtained from locations around the small lesion as well as one from the center of the lesion.
The available treatment options for cancerous lesions of the breast include various degrees of mastectomy or lumpectomy, radiation therapy, chemotherapy and combinations of these treatments. However, radiographically visible tissue features, originally observed in a mammogram, may be removed, altered or obscured by the biopsy procedure, and may heal or otherwise become altered following the biopsy. In order for the surgeon or radiation oncologist to direct surgical or radiation treatment to the precise location of the breast lesion several days or weeks after the biopsy procedure was performed, it is desirable that a biopsy site marker be placed in the patient's body to serve as a landmark for subsequent location of the lesion site. A biopsy site marker may be a permanent marker (e.g., a metal marker visible under x-ray examination), or a temporary marker (e.g., a bioresorbable marker detectable with ultrasound). While current radiographic type markers may persist at the biopsy site, an additional mammography generally must be performed at the time of follow up treatment or surgery in order to locate the site of the previous surgery or biopsy. In addition, once the site of the previous procedure is located using mammography, the site must usually be marked with a location wire which has a hook on the end which is advanced into site of the previous procedure. The hook is meant to fix the tip of the location wire with respect to the site of the previous procedure so that the patient can then be removed from the confinement of the mammography apparatus and the follow-up procedure performed. However, as the patient is removed from the mammography apparatus, or otherwise transported the position of the location wire can change or shift in relation to the site of the previous procedure. This, in turn, can result in follow-up treatments being misdirected to an undesired portion of the patient's tissue.
As an alternative or adjunct to radiographic imaging, ultrasonic imaging (herein abbreviated as “USI”) or visualization techniques can be used to image the tissue of interest at the site of interest during a surgical or biopsy procedure or follow-up procedure. USI is capable of providing precise location and imaging of suspicious tissue, surrounding tissue and biopsy instruments within the patient's body during a procedure. Such imaging facilitates accurate and controllable removal or sampling of the suspicious tissue so as to minimize trauma to surrounding healthy tissue.
For example, during a breast biopsy procedure, the biopsy device is often imaged with USI while the device is being inserted into the patient's breast and activated to remove a sample of suspicious breast tissue. As USI is often used to image tissue during follow-up treatment, it may be desirable to have a marker, similar to the radiographic markers discussed above, which can be placed in a patient's body at the site of a surgical procedure and which are visible using USI. Such a marker enables a follow-up procedure to be performed without the need for traditional radiographic mammography imaging which, as discussed above, can be subject to inaccuracies as a result of shifting of the location wire as well as being tedious and uncomfortable for the patient.
Placement of a marker or multiple markers at a location within a patient's body requires delivery devices capable of holding markers within the device until the device is properly situated within a breast or other body location. Accordingly, devices and methods for retaining markers within a marker delivery device while allowing their expulsion from the devices at desired intracorporeal locations are desired.